North Korea revealed a homegrown “underwater nuclear attack drone” for the first time via state media Friday and reported on cruise missile tests guided by leader Kim Jong Un in recent days, warning the U.S. and South Korea that an “actual nuclear crisis” is at hand.

The Korean Central News Agency (KCNA) stated that the underwater drone is named “Haeil” (해일) and that its mission is “​to stealthily infiltrate into operational waters and make a super-scale radioactive tsunami through underwater explosion to destroy naval striker groups and major operational ports of the enemy.”